Window-mounted domestic room air conditioners provide an effective and economical means for cooling the air in a limited living space. These units are a popular alternative to central air conditioning systems, which cool the entire household by circulating the conditioned air through the house central air duct system. The central air duct system often includes some form of air filtration system to remove airborne particulate matter from the recirculated air stream. Air filtration is desirable to provide a cleaner and healthier living environment in the house.
For these same reasons, it is desirable to provide air filtration means on window-mounted air conditioners. A filter may be located inside a window-mounted air conditioner housing directly behind the air inlet duct, so that air which is drawn into the air inlet by the air conditioner internal fan first passes through the filter element, and then passes through the heat exchange coil to be cooled before exiting to the room environment.
It is important that the air filter is changed or cleaned on a regular basis because after a period of time the filter will become partially clogged with trapped particles. When the filter becomes clogged, it reduces the flow of air into the unit, thereby reducing the effectiveness of the air conditioner. It is therefore desirable to provide some method of signalling that the filter is clogged and requires changing.
In the past, this problem has been addressed in a variety of ways. U.S. Pat. No. 3,263,403 discloses an air conditioner filter condition indicator that has a float inside a transparent tube on the front of the housing, such that when the filter is clogged the float is visible through a cutout window in the control knob to indicate that the filter requires changing. U.S. Pat. No. 3,201,772 discloses an air conditioner in which the increased air pressure against the clogged filter causes the filter element to drop onto a mechanical lever which causes a visual signal to be displayed in a window on the air conditioner housing.
Among the drawbacks of these prior systems are decreased visual aesthetics, since the indicator window or tube is always visible. Also of concern are the cost of the parts of the prior systems, the number of parts involved in such systems, the amount of modification required to the air conditioner housing to install a particular system, and the manufacturability of units incorporating such systems.